The Abortion Act allows termination at any stage of pregnancy if two doctors agree there is a "substantial risk" of the child being "serious handicapped".

But the scope of the term is left to the doctors' discretion, and some fear the definition of "handicap" is widening as scanning technology develops.

In 2003, a cleric instigated a legal challenge against the refusal of police to prosecute doctors who carried out a late abortion on a woman because she did not want a baby with a cleft palate.

The abortion was carried out when the woman, from Herefordshire, was more than 24 weeks pregnant.

Reverend Joanna Jepson, curate of St Michael's Church in Chester, had corrective surgery on a congenital jaw defect and believes that a cleft palate is not a serious handicap.

The Archbishop of Canterbury today made a rare public foray into the debate, warning that the British public no longer regards abortion as a last resort and is in danger of losing its "moral focus" on the issue.

Dr Rowan Williams told the Observer there is a growing belief that abortion is an "individual decision" and not "the kind of major moral choice that should involve a sharing of perspective and judgment".

Although the Archbishop was widely believed to oppose abortion, earlier public pronouncements on the issue had been obscure.

Josephine Quintavalle, of the Pro-Life Alliance, welcomed his contribution and called for a review of the current abortion law.

"The Abortion Act effectively discriminates against disabled people. What constitutes serious disability is in the eye of the beholder. It comes down to the idea of whether we have the right to make a list of who should live and who should die, what is serious and what isn’t," she said.

A Commons inquiry by the Science and Technology Committee is examining whether the 24-week upper time limit for an abortion should be reduced.

It is also considering whether the requirement for the written approval of two doctors should be scrapped, and whether nurses should be permitted to perform early-stage abortions.

The inquiry was partly provoked by the so-called "4D scans" of foetuses, developed by Professor Stuart Campbell, which showed them apparently smiling and crying in the womb.

Anne Quesney, the director of the pro-choice campaign group Abortion Rights, said: "No woman or doctor makes the abortion decision lightly, especially not at later gestation. Cleft lip palate and other conditions can be symptomatic of more serious and life threatening impairments.

"Those who are serious about reducing the number of abortions should be looking to countries such as Sweden and Holland where liberal abortion laws go hand in hand with good statutory sex and relationships education and widespread access to free contraception.

"Reducing the time limit for abortion would force a tiny number of vulnerable women to continue with impossible pregnancies."